This is the blog for Yale's undergrad course ANTH204:
An introduction to the patterns and processes of human genetic variation. Topics include: human origins and migration; molecular adaptations to environment, lifestyle and disease; ancient and forensic DNA analyses; and genealogical reconstructions.

Tuesday, December 13, 2011

A Small Step for Lungfish, a Big Step for the Evolution of Walking

Well, it looks as if it is once again time to completely rewrite how we think about the early evolution of land-dwelling creatures. That is because new information has come out on the walking abilities of the African lungfish, one of the more unlikely candidates for locomotion. Still, scientists at the University of Chicago have deduced the incredible ability of the lungfish to walk due to its very thin pelvic limbs. While this ability was previously thought to have originated with tetrapods, it now appears as if it may have been the earlier ancestors of this lungfish.

In fact, scientists are even now reexamining fossil tracks previously concluded to be left by tetrapods. Melinda Hale, an associate professor, now states that, "Aquatic animals with fundamentally different morphologies and that aren't tetrapods could potentially make very similar track patterns." But, why was this not discovered sooner? That lies in the structure of the lungfish's strangely thin limbs. When Heather King, the lead author the study, decided to monitor the movements of the lab's lungfish, she discovered that the lungfish could lift and propel itself on these tiny limbs.

It is indeed lucky to have a live specimen of such incredible genetic history to be able to work with hands-on in the lab. In fact, this was probably the only way scientists would have made this discovery. As King conceded, "If you were just to look at the bones, like you would with a fossil, you might not even know these motions could occur." The fact that it has this locomotive ability may be due to the change in gravity underwater. By filling up its front with air, the lungfish could become just buoyant enough to be able to bound and run as we now know it is able to do.